The present invention relates to an apparatus for minimising noise from air moving devices, such as fans, air blowers etc. In particular, the present invention relates to a fan unit which may be used with a filter.
It is common to control the number of particles in the air in a modern production and/or testing facility in order to ensure the quality of its output. Whether be it for wafer dies, compact discs or memory disk drives, effective fan filter units are needed to not only keep the particles contents within the clean room at acceptable levels but also to circulate the air to maintain a pleasant working environment for the clean room workers.
However, such powerful fan filter units create excessive noise. It is known to use insulation materials to line along a conduit to or within the fan filter units to reduce noise. However, over time, the particles or fiber from the insulation material are dislodged from the surface and contaminate the clean room facility.
The problem associated with fan filter noise is particularly exacerbated in confined spaces or enclosures such as a multi-story water fabrication plant. By confined space, the present invention envisages the height of the ceiling to be less than three meters. Low ceilings cause noise from fan filter unit to be particularly pronounced.
Previously, an apparatus which minimises noise from a fan filter unit has been suggested by the current applicant in WO 99/11984. However, the S-shaped baffles of this earlier design only allow the design to be used with fans which rotate with a predetermined orientation, i.e. either only clockwise or anti-clockwise.
The present invention attempts to address the above problem of reducing noise associated with a fan unit, without increasing contamination caused by the unit. The present invention also attempts to increase the power efficiency of such a fan unit. The invention also can be used regardless of whether the fan rotates in an anti-clockwise or clockwise direction.
The present invention provides a fan unit comprising
a fan blower configured to emit air in a plurality of directions in an air flow plane,
a pair of guides disposed on opposite sides of said fan blower in the said air flow plane to guide the flow of air between the two guides, each guide having and indent opposite said fan to accommodate said fan and each guide being symmetric about a symmetry plane perpendicular to the air flow plane formed through the centre of the fan and an indent, and upper and lower baffles at each end of the guides to direct air out of the unit, the baffles being arranged perpendicular to the direction of the plane of air with the lower baffle beneath the upper baffle the baffles being inclined with respect to one another, such that the distance between the baffles decreases in a direction away from the fan.
The symmetric shape of each guide with respect to the fan allows the guides to be used in the same positions regardless of the direction of orientation of the fan.
In addition to the indent, the guides are preferably provided with protrusions on either side of the indent, wherein the protrusions extend towards the opposite guide. Thus, each guide has a substantially xe2x80x9cWxe2x80x9d-type shape. Preferably, the guide has a smoothly varying profile at the indent and, more preferably at the protrusions. However, the noise-reduction properties may be partially achieved, using a guide with straight sections.
The configuration of the guides reduces the noise from the fan unit. Also, the configuration of the guides enhances the velocity of air circulating in the unit. Hence, a more efficient fan unit can be produced as a lower power can be used to drive the fan to achieve the same circulating air velocity.
The air in the fan filter unit moves between the two guides. Baffles are preferably located at either end of the guides. The baffles are provided to direct the air away from the fan and out of the fan unit.
There are a pair of baffles at each end of the guides. There is an upper baffle and a lower baffle with the lower baffle beneath the upper baffle. The vertical direction is taken to be the direction which is perpendicular to the plane of air emitted from the fan. The baffles are preferably inclined with respect to one another, such that the distance between the baffles decreases in a direction away from the fan. Preferably, the upper baffles are disposed at an angle of at least 40xc2x0 and at most 60xc2x0 to the direction of the plane of air. More preferably, they are arranged at an angle of about 45xc2x0 to the air flow plane.
The lower baffles are preferably arranged at an angle of at least 5xc2x0 and at most 15xc2x0 to the direction of the plane of air more preferably at about 10xc2x0 to the plane of air.
The baffles are located such that as the air leaves the guides, the air is reflected by the upper baffle onto the lower baffle, the lower baffle is positioned to direct the air out of an outlet.
Preferably, the fan unit comprises a housing which has a base plate and an upper housing located above the base plate, the fan and guides being located between the upper housing and lower base plate, the unit having side sections which may be integral with the upper housing. The side sections being locate at opposite ends of the guides, such that the baffles lie between the side sections and the ends of the guides.
In the above configuration, the base plate will preferably be located relative to the housing such that the separation between the base palate and the upper surface of the upper housing is smaller that the distance which the side sections protrude from the upper surface of the housing. There is also a gap between the side sections and the base plate to form the outlet of the fan unit. The gap between the side section of the housing and the base plate should, ideally be large enough to accommodate at least a part of the lower baffle in this gap.
The fan unit of the present invention is primarily intended for use in a clean room. Therefore, the unit preferably comprises a filter. Generally, this filter will be located below the base plate of the unit.
The guides and/or the baffles of the present invention will preferably be made from a solid material, more preferably a metal. The guides and/or baffles may also be perforated.